Use Cases - SafeSlingerProject/SafeSlinger-Media GitHub Wiki

An out-of-band channel is critical to confirmation that targeted surveillance is not possible within any given end-to-end encryption scheme. While key servers, social graphs, and Trust-On-First-Use models of public key exchange help defend against a wide array of mass surveillance techniques, targeted surveillance defense requires assurance that any given key can be proven to belong to the exact physical person we expect. The SafeSlinger exchange protocol is a generalizable scheme that can be used to detect Man-In-The-Middle attacks ranging from usable key fingerprint verification up to full, easy public key exchange.

Users

Who needs to authenticate digital key owners?

  • Journalists protecting sources
  • Activists protecting membership
  • Enterprise system administrators
  • Users making micro-payments between each other (or themselves)
  • Casual users desiring confirmation

Benefits to Users

  • UX can show which contacts and conversations are protected against targeted surveillance.
  • Allows convenient verification for real time meetings with phones handy.
  • Allows convenient verification for real time video chat or telephone calls.
  • Protocol messages can be transmitted in the background.
  • Avoids having to read hex fingerprints, less prone to mistakes.
  • Allows remote verification, avoids having to be local for QR/NFC/BT channels.

Benefits to Service Providers

  • Adding a competitive security feature.
  • Knowledge which accounts are physically verified out of band.
  • Physically verified accounts can unlock additional security bonuses like secure introductions or forwarding trust.
  • Bonuses could be used to encourage end to end verification.
  • Allows provider to free up auditing and validation resources.
  • More Benefits!

Scenario Examples

These are just some examples of messaging services that provide end-to-end secure messaging. Centralized services have the ability to group users via a central server, while decentralized services do not know how many or which users are communicating in a group or pair.

Centralized

  • TextSecure/Signal (sans SMS), WhatsApp, Peerio
  • Jabber/XMPP IM: ChatSecure, Adium, Conversations

Decentralized

  • SafeSlinger Messenger
  • OpenPGP e-mail managers: OpenKeyChain, Enigmail, GPGTools, GPG4Win, Google end-to-end

UX for Centralized Device Messaging

  1. Alice and Bob enroll in an end to end encrypted messaging service.
  2. Alice selects contact Bob and a Confirm Security option.
  3. The client suggests and may assist Alice with opening a audio or video call to Bob, or she may choose to meet Bob in person.
  4. Bob selects a Ready to Confirm Security notification on his device.
  5. Alice's and Bob's client each show 3 sets of word phrases.
  6. Alice and Bob use the video channel to converse and find, then select, the matching phrase they share.
  7. Alice's and Bob's client each report the messaging security as either secure or under surveillance.

UX for Centralized Video Conferencing

  1. Alice and Bob enroll in and begin an end to end encrypted video conference.
  2. Alice selects the Confirm Security option on her client.
  3. Alice's and Bob's client each show 3 sets of word phrases.
  4. Alice and Bob use the video channel to converse and find, then select, the matching phrase they share.
  5. Alice's and Bob's client each report the video conference security as either secure or under surveillance.

UX for Decentralized Messaging

  1. Alice and Bob generate their public keys.
  2. Alice selects contact Bob and a Confirm Security option.
  3. The client suggests and may assist Alice with opening a audio or video call to Bob, or she may choose to meet Bob in person.
  4. Bob selects a Ready to Confirm Security notification on his device.
  5. Alice and Bob choose and submit the number of users in the exchange.
  6. Alice's and Bob's client each show a unique, low-entropy grouping number.
  7. Alice and Bob use the video channel to converse and find, then enter, the lowest grouping number.
  8. Alice's and Bob's client each show 3 sets of word phrases.
  9. Alice and Bob use the video channel to converse and find, then select, the matching phrase they share.
  10. Alice's and Bob's client each report the messaging security as either secure or under surveillance.

Potential Options

  • 3-word PGP word list used currently, but can be changed to any word list or other comparable verbal/visual metric that offers sufficient entropy of 24-bits.
  • When implementing internally, there is no need to standardize words or outside use, so use the word list you like.
  • Group exchange can scale to 63 users at current entropy of the 24-bit PGP word list.